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X-ray Reflectometry

XRR = X-ray-reflectometry also known as X-ray reflectivity or X-ray specular reflectivity

 

Specular X-ray Reflectivity (XRR), a technique related to X-ray Diffraction (XRD), is becoming a widely used tool for the characterization of thin-film and multilayer structures. X-ray scattering at very small diffraction angles allows characterization of the electron density profiles of thin films down to a few tens of Ǻ

When X-rays strike a surface at glancing incidence they can reflect off the surface. However, if the surface is rough or covered by a film, then the X-ray reflectivity of a surface can change. XRR takes advantage of this effect by measuring the intensity of X-rays reflected from a surface as a function of angle. Thin films on a surface can give rise to oscillations of the X-ray intensity with angle

XRR method involves monitoring the intensity of the x-ray beam reflected by a sample at grazing angles.

A monochromatic x-ray beam of wavelength λ irradiates a sample at a grazing angle ϖ and the reflected intensity at an angle 2θ is recorded by a detector.

 

The main applications are the determination of :

*film thickness (maximum film thickness ~300nm)

*interface/surface roughness

*density for thin films and multi-layers (the order of layers and their approximate compositions are needed in order to provide accurate density results)